Local scientist believes Voyager I went 'over the edge'

HARDING TWP. - For more than 25 years, the Voyager I spacecraft
has been hurtling toward the outer reaches of the solar system, far
beyond the point where its designers expected it to break down.

Now some scientists, including astrophysicist Lou Lanzerotti of
Brook Drive North, believe it has actually "gone over the edge,"
having passed the orbit of Neptune to reach a point where the solar
wind bumps up against the vastness of interstellar space.

At this boundary about 8 billion miles from earth, Voyager I may
actually have entered the heliosheath, a nebulous beltway where the
solar wind is abruptly slowed by interstellar pressure, causing a
phenomenon known as "termination shock."

Lanzerotti and his colleagues believe Voyager temporarily
entered the unexplored region beyond the sun's magnetic field for
about 200 days, but because this boundary keeps shifting with
changes in solar activity, it has moved outward since then, leaving
Voyager I back within the supersonic solar wind.

Differing Opinions

But not all scientists agree that the spacecraft has reached
termination shock. There are three schools of thought, all inferred
from measurements of particle activity and magnetic fields taken by
the three instruments on Voyager I and beamed back to earth.

Some scientists believe the spacecraft has not yet reached the
heliosheath, and a third group still has not formed an opinion
about what is being observed on Voyager I.

Lanzerotti said he and a colleague designed one of the
instruments on board in the mid-1970s to measure the lowest level
energy particles other than those found in solar wind. They did a
lot of the design work at Bell Labs, where Lanzerotti worked as a
research scientist, and built the device at Johns Hopkins Applied
Physics Lab in Laurel, Md.

A particle accelerator at Rutgers University was used to
calibrate the instrument, which no one believed would last as long
as it has, Lanzerotti said. It is smaller than a breadbox and
swings around 360 degrees to measure both the energy and the
direction of particle movements.

A second instrument developed by another team of scientists
measures somewhat larger particle behavior and the third instrument
monitors the magnetic field. There is a fourth instrument on board,
designed to measure solar wind speed, and it might have provided
the tie-breaking data, but it is no longer functioning.

One thing is certain. The spacecraft has reached a region of the
solar system unlike any encountered before, and far beyond where
any manmade object has ever traveled.

Scientists will continue to monitor data from Voyager I as it
continues its journey over the next couple of years or even longer,
Lanzerotti said. Its radioisotope-generated fuel is expected to
last till around 2020.

Beyond the heliosheath, the spacecraft will continue to collect
data to help humankind understand the nature of interstellar space,
he said.

In the meantime, Voyager II, which was launched a month after
Voyager I, is trailing behind its predecessor by about 3,000
kilometers, on a separate trajectory, with its solar wind-measuring
instrument still intact. Eventually, it also is expected to reach
the threshold of the solar system and add to scientific
understanding about what's out there.

Whether or not Voyager I has passed into the heliosheath as yet,
the program has disproved some earlier theories about the solar
system, Lanzerotti said.

Originally planned as sort of a grand tour of Jupiter and Saturn
and only expected to last five to 10 years, the mission surprised
everyone when Voyager I bounced off Saturn's gravity and just kept
going. In fact, things were going so well that NASA continued to
support the mission, which ended up visiting all of the outer
planets except for Pluto.

"About two years ago, NASA considering turning off Voyager for
budgetary reasons," Lanzerotti said. "It costs about $5 million per
year to operate it. But there was such an uproar from the research
community that NASA backed down."

In the 1950s, when the space program began to ramp up,
scientists believed that space was empty, devoid of particle
activity, and in the early 1960s a scientific paper hypothesized
that interstellar space began at Mars, Lanzerotti said.

"By a funny quirk, when I was in college in the late 1960s I
wrote a paper based on my analysis of optical data from Jupiter,"
he said. "I thought the boundary was probably nearer the orbit of
Jupiter or near the orbit of Saturn, varying with the solar
cycles.

"When Pioneer arrived in the 1970s and then Voyager in 1979, it
became quite clear that all the papers were wrong. But that's how
science advances. We make proposals and then we test them.

"That was the most wrong thing I've ever predicted and I'm proud
of it."

Lanzerotti is retired from Bell Labs, where he began his career
in 1965 after earning his undergraduate degree at the University of
Illinois at Champagne and his doctorate degree at Harvard
University, Cambridge, Mass.

He is a distinguished research professor at New Jersey Institute
of Technology in Newark. During the George H.W. Bush
administration, he was a member of Vice President Dan Quail's Space
Policy Board and served for nearly 10 years as a member of the NASA
Advisory Council.

Lanzerotti currently is serving his fourth term on the Harding
Township Committee.

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